An induction motor draws 50 A from a 380 V three-phase line at a lagging power factor of 0.9. Its stator and rotor copper losses are 1000 and 500, respectively. Its core losses are 650 W, the friction and windage losses are 200 W, and the stray losses are 250 W. Determine the following:
a. Airgap power
b. Mechanical power developed
c. The shaft output power in W
d. The efficiency of the motor
2. Corrected_text: A three-phase two-pole, 25 hp, 380 V, 60 Hz, wye-connected induction motor has the following constants in ohms per phase referred to the stator: R1=0.525, R2=0.295, X1=1.75, X2=0.8, Q Xm=20.5.
The total rotational losses are 1850 W and are assumed to be constant. The core loss is lumped in with the rotational losses. For a rotor slip of 3.33% at the rated voltage and rated frequency, determine the following:
a. The speed in rpm
b. The stator current
c. The power factor
d. The developed power and output power
e. The developed torque
f. The efficiency
3. Corrected_text: A three-phase six-pole 75 hp, 480 V, 60 Hz, wye-connected induction motor has the following parameters: R1=0.245, R2=0.198, X1=0.975, X2=0.72, Xm=14.5.
Determine the following:
a. The slip at which maximum torque is developed
b. The speed at which the maximum torque is developed
c. The maximum torque developed
d. The starting torque developed
e. The speed at which the maximum torque is doubled
f. The maximum torque developed if rotor resistance is doubled
